TITLE:   GCN CIRCULAR
NUMBER:  38872
SUBJECT: EP250109a: SVOM/VT optical candidate
DATE:    25/01/09 13:56:18 GMT
FROM:    Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>

SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, H. Sun, L. P. Xin, C. Wu, X. H. Han, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV)

report on behalf of the SVOM team:

The SVOM/VT conducted a ToO follow-up observations of EP250109a triggered by EP-WXT(Li et al., GCN 38864) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, from 4.13 hours to 4.80 hours after the burst. 

An uncatalogued source was detected within the errorbox of FXT (Li et al.,GCN 38864) in VT_R stacked image, compared to the Pan-STARRS catalog. This source is the only one source within the error box. The brightness of the source was estimated to be VT_R=22.34+/-0.15 in AB magnitude at the mid time of 4.47 hours post the burst, with a total exposure time of 38*100 seconds. The source was not detected in VT_B stacked image down to a 3 sigma upper limit of 23.6 mag with a total exposure time of 21*100 sec.

The source is located at RA, Dec = 88.80672, -12.49599 deg, which is equivalent to:
RA (J2000) : 05:55:13.61
Dec (J2000): -12:29:45.6
with an uncertainty of 0.5 arcsec.

We are waiting for more data to confirm the fading of the source. 

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.